Three-phase transformer



Nov. 12, 1946. R. D. NELSON THREE PHASE TRANSFORMER Original Filed May 17, 1943 I N V EN TOR flaw/m0 Mao/v ATM/P/VEX Patented Nov. 12, 1946 UNITED STATES PATENT OFFICE 2,411,104 THREE-PHASE TRANSFORMER Rolland D. Nelson, to Line Material Hales Corners, Wis., assignor Company,

South Milwaukee,

Wis., a corporation of Delaware Original application May 17, 1943, Serial No.

1944, Serial No. 529,101

This invention relates to three phase transformers and is a division of my application filed May 17, 1943, Serial No. 487,202, now Patent No.

customary type of core for the three phase transformer. These stacked types of three phase transformers were hard to repair in case of failure of one of the coils since it was necessary to remove the entire stacked end portion in order to remove the defective coil. Even in the initial stacking operation some mechanical stress was always imparted to the core pieces in the practical manufacture of the transformer and this reduced the efiiciency of the transformer. Also in the stacked core construction it is necessary for the magnetic flux to travel cross grain at the corners of the core and this, in addition to the defect hereinabove noted, entailed a certain amount of loss in the core of the transformer.

This invention is designed to overcome the above noted defects, and objects of this invention are to provide a novel form of three phase transformer which has its core structure formed of wound magnetic ribbon, which is wound into closed cores, which are thereafter cut into sections and such sections used in the completed device, in which no unusual care is required in the assembly of the parts of the device, in which no bending, machining or other working of the core structure is required after annealing, and in which short-circuiting of the laminations is avoided.

Further objects of this invention are to provide a three phase transformer which in its preferred form is composed of cores which are formed of wound magnetic ribbon subsequently cut into sections and-so arranged that an efficient three phase transformer core structure results, and in which the conducting windings may be very readily wound in a simple andprdinary manner upon the core sections without requiring any special machine other than the usual type of winding machines for winding the conducting windings.

Divided and this application April 1,

4 Claims. (Cl. 356) This invention in its broadest aspect permits the use of stacked magnetic laminations or of wound cores formed of magnetic ribbon which are subsequently cut into parts after winding, the resulting magnetic core structure Whether formed of stacked laminations or wound cores subsequently cut into sections being laminated throughout its entire extent.

Further objects are to provide a three phase transformer in which there are relatively few joints in the core structure, in which the joints in the core structure are so formed that a substantially edge to edge contact of the adjacent laminations is obtained, thereby materially reducing the reluctance of the magnetic path, and in which these results are obtained in a very simple manner and with a very small amount of work required in the manufacture of the device.

Further objects are to provide a novel con- I struction of three phase transformer in which the losses are relatively small, and in which a very good space factor is obtained for the conducting winding.

Further objects are to provide a novel form of three phase transformer which is simple to manufacture and in which the number of operations required in its production is materially reduced.

An embodiment of the invention is shown in the accompanying drawing, in which:

Figure 1 is a plan view of the transformer with parts broken away and parts in section and showing in dotted outline the transformer casing.

Figure 2 is an elevation of the transformer with parts broken away.

Figure 3 is a perspective view of the core structure.

Referring to the drawing, it will be seen that the transformer core structure comprises three identical core sections indicated by the reference characters 5, 2 and 3. Each of these core sections is formed by winding 9. closed core of magnetic ribbon and cutting it across, preferably cutting it in half. The material used in making the cores is any suitable magnetic ribbon. It is preferable to use silicon steel, which may be either hot rolled or cold rolled, as this material has been found highly efficient in the manufacture of transformers.

As stated, the magnetic ribbon is wound to form a closed, continuous core and thereafter is cut across to form a pair of sections. These sections are arranged with their side faces in substantial contact. They may be in actual physical contact or they may be spaced apart by the an moi tween the end portions of adjacent core sections.

It is preferable to grind the juxtaposed faces of these sections to get true, flat faces.

a v I obvious that a core section can be placed in a in the manufacture of the core sections, aiter the sections have been tightly wound as closed -cores and out, preferably in hell, as described hereinabove, and after the appropriate faces have been ground, they are annealed while they are held in shape. After annealing no further working of the cores takes place in any manner whatsoever. Any wire edges that may be left are usually burned ofi during annealing, but if any should be found to remain, they may be removed by a wire brnsh'or in any other suitable man ner. After the core sections have been annealed,

, they are then separately wound to provide their primaries and secondaries, which will hereinafter pair of upright angle irons l which are held in clamping relation by means of the upper and lower tie bolts ii. Insulating-sheets 9 are positioned between the clamping means and the adjacent core sections to prevent short-circuiting across the ends of the core sections and it is preferable to provide an insulating sleeve indicated at id on the tie bolts. his to be noted that the tie bolt structure, that is to say, the bolt with the insulating sleeve lil,'engages the upper and lower faces of the outermost layers oi the core sections and thus prevent these layers from being distorted outwardly out of position.

It is to be noted particularly that the side edges of the adjacent laminations of the end portions of successive core sections are arranged in parallelism so that they have either an edge to edge contact or an edge to edge juxtaposition. By having the edge to edge contact or edge to edge juxtaposition between the laminations of the central and outer cores, a material reduction in the reluctance of the magnetic path results.

It is to be noted that the magnetic flux travels lengthwise of the magnetic ribbon in substantially all portions of the core structure and this is the path having minimum magneticreluctance. However, there is a small portion of the magnetic flux path where the flux travels crosswise of the magnetic ribbon where it passes from the end portions of one core section to the end portions of the adjacent core section. This path of cross travel oi? the flux is very short and is confined to a very limited portion of the entire flux path;

It will be seen, therefore, that a transformer has been provided by thisinvention which has a very small magnetic reluctance for the flux travel and which is extremely simple to make and which utilizes the advantages of wound magnetic cores formed from magnetic ribbon though allowing the conducting winding assemblies to bewound in the ordinary simple manner without requiring any special processes or special machines. In winding the conducting winding assemblies, it is lathe or other suitable machine and the conducting winding wound directly thereon in a very simple manner.-

-' This invention, therefore, provides a novel type of three phase transformer construction which,

utilizes the wound core principle but which nevertheless provides. a very simple way of directly winding the conducting winding assemblies'on each of the core sections.

It is to be noted further that the symmetrical arrangement of the core sections makes the transformer ilt readily within an ordinary cylindricai transformer casing.

While it is much preferred to form the core sections in the mmner hereinabove outlined, nevertheless it is to be understood that the core sections may be built up from laminations of succeedingiy greater lengths and shaped as shown in the drawing, and therefore it is to be understood that whenever the expressions lamina tions or magnetic laminations are employed, it is" intended that these expressions shall not be limited to stacked laminations but shall include any laminated structure whether it is formed by winding magnetic ribbon or by stacking magnetic laminations.

It will be seen that by forming the coresections in either of the ways hereinbei'ore described,

' than limiting, as the invention may be variously former comprising three separate and identical core sections each having a main portion adapted to receive a conducting 'windingassembly and having outwardly projecting end mrtions at opposite ends of the main portion, the side faces of the end portions of theicore' sections being in close juxtaposition; said core sections being formed of laminationswith the side edges of the laminations ofthe end portions of a core section arranged in substantial parallelism with the side edgesof the laminations oi the end portions of the next adjacent core section and with the sideedges of the laminations in the said one coreisection in substantial edge-to edge contact with the side edges of the laminations of the end portions of adjacent core sections.

2. A core construction for a three phase transiormer comprising three separate core sections each having a main portion adapted to receive a conducting winding assembly and having out= wardly projecting end portions at opposite ends of the main portion, the side faces of the end portions of the core sections being arranged in close juxtaposition, each of said core sections being formed of a plurality of laminations ar= ranged in nesting relation with successive lami= nations enclosing preceding laminations, the core sections being arranged with the end portions of one core section located between the end portions of the other'two core sections.

3. A core construction for a three phase trans= former comprising three separate core sections each having a main portion adapted to receive a conducting winding assembly and having outweirdlyv projecting end portions at opposite ends a 5 of the main portion, the side faces otthe end portions of the core sections being arranged in close juxtaposition, each of said core sections being formed of a plurality of laminations arranged in nesting relation with successive laminations enclosing preceding laminations, the core sections being arranged with the end portions of one core section located between the end portions of the other two core sections and with the sideing a main portion adapted to receive a conducting winding assembly and having outwardly projecting end portions at opposite ends of the main portion, the core sections being arranged with the end portions of one core section locdted between the end portions of the other two core sections and with the side faces of the end portions of successive sections in close juxtaposition and with the side edges of the laminations in the said one core section in substantial edge-toedge contact with the side edges of the laminations of the end portions of adjacent core sections, the said one section being reversed with respect to the other two sections. v

ROI-LAND n. NELSON." 

